JPH07211571A - Manufacture of thin-film coil - Google Patents

Abstract

PURPOSE:To obtain a thin-film coil in which a thick film for a high-quality and high-Q-value coil conductor is realized in the small number of processes by a method wherein a photoresist is used as a plating mask, the coil conductor is electrodeposited and formed in a part in which a plated substratum electrode is exposed, the plated substratum electrode other than the part of the coil conductor is etched and a resin is coated. CONSTITUTION:An SiO2 film 2 is formed on a silicon substrate 1, and a thin-film plated substratum electrode 11 which uses W as a metal material is vapor- deposited in the whole region on the surface. Then, the plated substratum electrode 11 is coated with a positive-type photoresist, the photoresist is exposed and developed, and a selective plating mask 12 corresponding to a desired coil pattern is formed. In succession, a Cu electrolytic plating operation is performed, and coil conductors 13 are electrodeposited and formed selectively on the exposed face of the plated substratum electrode 11. Then, the mask 12 is stripped, a plasma etching operation is conducted to the plated substratum electrode 11, and parts other than parts 11a covered with the coil conductors 13 are removed. After that, the whole face of the substrate 1 is coated with a polyimide resin 14 so as to cover the coil conductors 13.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention is applied to, for example, a DC-DC converter, and a monolithically formed ultra-compact thin film inductor, thin film transformer or the like is formed on a silicon substrate on which a semiconductor element is formed. The present invention relates to a method of manufacturing a thin film coil.

[0002]

2. Description of the Related Art As a method for forming a microminiature thin film inductor, thin film transformer, etc. on a substrate, the method disclosed in Japanese Patent Laid-Open No.
As disclosed in Japanese Laid-Open Patent Publication No. 1511 211, a method of alternately laminating a paste-formed magnetic layer and a screen-printed coil conductor pattern on a substrate through an insulating layer and firing the same is generally adopted. . However, when the thin film coil is monolithically formed on the silicon substrate on which the semiconductor element is built, the above method has a risk that the semiconductor element built on the substrate side is thermally destroyed due to the high firing temperature. However, the following manufacturing method is known as an alternative method.

Example 1: As disclosed in Japanese Patent Application Laid-Open No. 2-123706, a semiconductor device manufacturing process is adopted in which an insulating layer, a magnetic layer and a conductor layer are repeatedly sputter-deposited and photolithographically operated on a substrate. To form a thin film coil. FIG. 2 shows a method of manufacturing a laminated thin film transformer that employs such a manufacturing method. A SiO ₂ film 2 as an insulating film is formed on a silicon substrate 1 on which a semiconductor element is formed.
Is formed by a sputtering method, and a film thickness of 10 μm is further formed thereon.
The Cu film 3 and the Ta film 4 each having a thickness of about m are formed in an overlapping manner (FIG. 2).
(See (a)). Next, the coil conductor 3a having a spiral pattern is formed on the Cu film 3 by N ₂ ion beam etching using the Ta film 4 as a mask (see FIG. 2B). Subsequently, an interlayer insulating film 5 is coated on the entire surface of the substrate so as to cover the coil conductor 3a, a magnetic film (for example, CoZrRe) 6 is layered thereon (see FIG. 2 (c)), and then the magnetic film 6 is covered. Then, the upper coil conductor 3b is formed through the interlayer insulating film 5 by the same procedure as described above (see FIG. 2D).
The magnetic film 6 on the upper side is layered through to complete the thin film transformer (see FIG. 2E).

Example 2: A thin film coil is formed by using a thin film technique and a selective plating method, as disclosed in Japanese Patent Laid-Open No. 2-126610. That is, as shown in FIG. 3, a SiO ₂ film 2 is formed on a silicon substrate 1 on which a semiconductor element is built.
After depositing, a multilayer metal film 7 such as Ti, Cr, Pd and Ni, Cu, Ag etc. to be a plating base electrode is formed on the entire surface of the SiO ₂ film 2 by the sputtering method (see FIG. 3 (a)). After that, the multilayer metal film 7 is processed by a normal photolithography method to pattern-form a spiral plating base electrode 7a corresponding to the coil conductor (see FIG. 3B). Next, a polyimide or polyamide resin insulating film 8 is coated on the surface of the substrate 1 so as to cover the underlying electrode 7a, and the insulating film 8 is etched to remove the upper surface portion of the underlying electrode 7a (see FIG. )), A metal such as Ag, Cu, Au is electroplated or electrodeposited by electroless plating on the exposed portion of the base electrode 7a using the insulating film 8 as a plating mask to form the coil conductor 9. (See FIG. 3D). After that, the same polyimide or polyamide resin is coated on the insulating film 8 so as to cover the coil conductor 9, and a window for drawing out a terminal is opened at a position corresponding to the end of the coil conductor 9 to lead the lead. Wire 10 (FIG. 3E).

[0005]

The conventional semiconductor coil manufacturing method described above has the following problems. That is, in the manufacturing method of Example 1 (FIG. 2), a thick conductor film having a film thickness of about 10 μm is vapor-deposited on the entire surface of a silicon substrate so as to improve the Q value of the coil, and then the coil is formed on the conductor film by a photolithography method. The method of patterning the conductor is adopted. Then, when the conductor film is vapor-deposited on the entire surface of the substrate, stress is generated and warps occur in the substrate (the larger the film thickness of the conductor film, the larger the generated stress and warp). As a result, the subsequent photolithography process is hindered. Further, the method of depositing a Cu film directly on the SiO ₂ film by the sputtering method has a problem in adhesion.

On the other hand, in the manufacturing method of Example 2 (FIG. 3), since the multilayer metal film is used for the plating base electrode, the following problems remain in the process. That is, (1) In order to form the base electrode by etching the multilayer metal film, it is necessary to carefully select the etching solution, which is troublesome. (2) The number of steps is increased because the manufacturing of the coil requires a photomask for processing the plating base electrode and a photomask for processing the polyimide or the polyamide that serves as the plating mask of the coil conductor.

(3) When the coil conductor is formed by electrolytic plating in order to process the plating base electrode corresponding to the coil pattern before forming the coil conductor, the plating base electrode is formed on the entire surface of the substrate. The electric field distribution becomes non-uniform as compared with the formed state, which causes variations in the plating thickness of the coil conductor. Moreover, since the electroless plating method cannot sufficiently increase the plating thickness, it is difficult to produce a thin film coil having a high Q value.

The present invention has been made in view of the above points, and an object of the present invention is to solve the above problems and to realize a high-quality coil conductor having a high Q value and a thick film with a small number of steps. It is to provide a method for manufacturing a thin film coil.

[0009]

According to the present invention, the above object is to form a plating underlayer electrode as a single-layer thin film conductor layer on the surface of a substrate, and to apply a photoresist to the surface of the plating underlayer electrode. , A step of forming a selective plating mask corresponding to the pattern of the coil conductor by photolithography, and the electrode of the coil conductor is selectively electrodeposited by electrolytic plating on the exposed portion of the plating base electrode using the photoresist as a plating mask. A step of forming, a step of removing the plating mask and then removing the plating base electrode other than the coil conductor forming portion by etching, and a step of covering the coil conductor with a resin to be an insulating layer on the substrate It can be achieved by a manufacturing method including and.

Further, in carrying out the above-mentioned manufacturing method,
Al, Cr, Ti, Ta, Zr, Ru,
It is preferable to use either Mo or W, and further use Cu, Ag, or Au as the metal material of the coil conductor.

[0011]

According to the above-described manufacturing method, the coil conductor is formed by the electroplating method with the single-layer thin film conductor layer serving as the plating base electrode formed on the entire surface of the substrate. A uniform electric field distribution in the coil conductor allows uniform formation of the coil conductor with less variation in film thickness. Further, since the plating base electrode is a single layer, high adhesion is secured with the coil conductor, and the base electrode can be easily processed. Especially as a metal material for plating base electrode
By using metals such as l, Cr, Ti, Ta, Zr, Ru, Mo, and W that are relatively easily oxidized (the free energy for oxide formation is small), the electrical resistance is low and Cu, Ag, Au, etc. A coil conductor having good adhesion to a plating metal and having a large film thickness can be selectively formed by using the plating mask in combination with a photoresist.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIG. In the drawings of the embodiments, the same members corresponding to FIGS. 2 and 3 are designated by the same reference numerals. 1A to 1E show the manufacturing method of the present invention for manufacturing an air-core thin film coil in the order of steps. In this embodiment, first, a silicon substrate 1 having a semiconductor element formed therein is formed with an SiO ₂ film 2 having a thickness of 0.8 μm on the upper surface thereof, and further, W is made of a metal material over the entire upper surface. A thin plating base electrode 11 having a thickness of 0.3 μm was deposited by a sputtering method. (Fig. 1
(A)) Next, using a spin coater (rotation speed 800 rpm, coating time 10 seconds), a film thickness of 25 is formed on the plating base electrode 11.
μm positive photoresist (Tokyo Ohka: PMER P-AR9
00), and then exposed and developed using a photomask to form a selective plating mask 12 corresponding to a desired coil pattern. (FIG. 1 (b)) Subsequently, the substrate was immersed in a hydrofluoric acid solution (concentration: 30%) for 30 seconds for pretreatment, washed with water, and then subjected to Cu electrolytic plating to form a plating base electrode 11
A coil conductor 13 having a thickness of 25 μm was selectively electrodeposited on the exposed surface of (1) (FIG. 1 (c)). The Cu plating solution is MICR
OFAB Cu200, the substrate 1 was immersed in the cathode side, a phosphorus-containing copper electrode was set in the anode side, and current was supplied at a current density of 4 A / dm ² for about 25 minutes for plating.

Next, after the selective plating mask 12 was peeled off, the plating base electrode 11 was subjected to plasma etching with SF ₆ gas to remove portions other than the portion 11a covered with the coil conductor 13. (FIG. 1 (d)) After that, a polyimide resin 14 serving as an insulating layer is applied to the entire surface of the substrate 1 so as to cover the coil conductor 13, and a window is opened in a portion serving as a coil terminal, and then the lead 10 is wired. To complete the thin film coil.
(FIG. 1 (e)) Although the illustrated example illustrates the air-core thin-film coil, the thin-film transformer is manufactured by repeating the steps of forming the magnetic film and the upper coil conductor as in the case of FIG. Of course you can.

Further, as the metal material of the plating base electrode 11, W and Mo used in the illustrated embodiment are the most suitable because they can be easily processed by the dry etching method using SF ₆ gas or the like. , Ta, Ti, Cr, Zr, Ru, etc. can also be adopted. Since Ti and Zr have high specific resistance, it is advisable to take some measures such as increasing the film thickness to lower the electrical resistance during plating. In addition to Cu, Ag and Au can be used as the metal material of the coil conductor.

[0015]

As described above, according to the manufacturing method of the present invention, by simply selecting the material of the thin film conductor layer serving as the plating undercoating electrode of the coil conductor, the plating undercoating electrode can be formed as compared with the conventional method. The thin film coil with high Q value and excellent adhesion of
It can be produced at low cost and with good yield.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a method of manufacturing an air-core thin film coil according to a first embodiment of the present invention, in which (a) to (e) are manufacturing process diagrams shown in the order of processes.

FIG. 2 is an explanatory diagram of a method of manufacturing a laminated thin film transformer according to a conventional technique, in which (a) to (e) are manufacturing process diagrams shown in the order of processes.

FIG. 3 is an explanatory view of a method for manufacturing an air-core thin film coil of a conventional example different from that of FIG. 2, and (a) to (e) are manufacturing process diagrams shown in the order of processes.

[Explanation of symbols]

1 Silicon Substrate 2 SiO ₂ Film 11 Plating Base Electrode 12 Selective Plating Mask 13 Coil Conductor 14 Resin

Claims (3)

[Claims] 1. A step of forming a plating underlayer electrode as a single-layer thin film conductor layer on the surface of a substrate, and a photoresist is applied on the surface of the plating underlayer electrode to correspond to a coil conductor formation pattern by photolithography. A step of forming a selective plating mask, and a step of electrodeposition forming a coil conductor by an electrolytic plating method selectively on a portion where the plating base electrode is exposed using the photoresist as a plating mask,
After removing the plating mask, a step of etching and removing the plating base electrode other than the coil conductor forming portion, and a step of covering the coil conductor with a resin to be an insulating layer on the substrate are included. A method for manufacturing a thin film coil, which is characterized. 2. The manufacturing method according to claim 1, wherein the metal material of the plating base electrode is Al, Cr, Ti, Ta, Zr, Ru, Mo, W.
2. A method for manufacturing a thin film coil, characterized in that 3. The method for manufacturing a thin film coil according to claim 1, wherein the metal material of the coil conductor is any one of Cu, Ag and Au.